Phase space density analysis of outer radiation belt electron energization and loss during geoeffective and non-geoeffective sheath regions

2021 ◽  
Author(s):  
Milla Kalliokoski ◽  
Emilia Kilpua ◽  
Adnane Osmane ◽  
Allison Jaynes ◽  
Drew Turner ◽  
...  
Keyword(s):  
Phase Space ◽  
Energetic Electron ◽  
Electron Content ◽  
Phase Space Density ◽  
Geomagnetic Disturbances ◽  
Interplanetary Coronal Mass Ejections ◽  
Outer Radiation Belt ◽  
Space Density ◽  
Sheath Region ◽  
Chorus Waves

<p>The energetic electron content in the Van Allen radiation belts surrounding the Earth can vary dramatically on timescales from minutes to days, and these electrons present a hazard for spacecraft traversing the belts. The outer belt response to solar wind driving is however yet largely unpredictable. Here we investigate the driving of the belts by sheath regions preceding interplanetary coronal mass ejections. Electron dynamics in the belts is governed by various competing acceleration, transport and loss processes. We analyzed electron phase space density to compare the energization and loss mechanisms during a geoeffective and a non-geoeffective sheath region. These two case studies indicate that ULF-driven inward and outward radial transport, together with the incursions of the magnetopause, play a key role in causing the outer belt electron flux variations. Chorus waves also likely contribute to energization during the geoeffective event. A global picture of the wave activity is achieved through a chorus proxy utilizing POES measurements. We highlight that also the non-geoeffective sheath presented distinct changes in outer belt electron fluxes, which is also evidenced by our statistical study of outer belt electron fluxes during sheath events. While not as intense as during geoeffective sheaths, significant changes in outer belt electron fluxes occur also during sheaths that do not cause major geomagnetic disturbances.</p>

Substorm Injections as a Source of Relativistic Electrons in Earth’s Outer Radiation Belt

2020 ◽  
Author(s):  
Drew Turner ◽  
Ian Cohen ◽  
Kareem Sorathia ◽  
Sasha Ukhorskiy ◽  
Geoff Reeves ◽  
...  
Keyword(s):  
Phase Space ◽  
Plasma Sheet ◽  
Radiation Belt ◽  
Energetic Electron ◽  
Local Source ◽  
Relativistic Electrons ◽  
Phase Space Density ◽  
Outer Radiation Belt ◽  
Space Density ◽  
Van Allen Probes

<p>Earth’s magnetotail plasma sheet plays a crucial role in the variability of Earth’s outer electron radiation belt. Typically, injections of energetic electrons from Earth’s magnetotail into the outer radiation belt and inner magnetosphere during periods of substorm activity are not observed exceeding ~300 keV.  Consistent with that, phase space density radial distributions of electrons typically indicate that for electrons below ~300 keV, there is a source of electrons in the plasma sheet while for electrons with energies above that, there is a local source within the outer radiation belt itself.  However, here we ask the question: is this always the case or can the plasma sheet provide a direct source of relativistic (> ~500 keV) electrons into Earth’s outer radiation belt via substorm injection? Using phase space density analysis for fixed values of electron first and second adiabatic invariants, we use energetic electron data from NASA’s Van Allen Probes and Magnetospheric Multiscale (MMS) missions during periods in which MMS observed energetic electron injections in the plasma sheet while Van Allen Probes concurrently observed injections into the outer radiation belt. We report on cases that indicate there was a sufficient source of up to >1 MeV electrons in the electron injections in the plasma sheet as observed by MMS, yet Van Allen Probes did not see those energies injected inside of geosynchronous orbit.  From global insight with recent test-particle simulations in global, dynamic magnetospheric fields, we offer an explanation for why the highest-energy electrons might not be able to inject into the outer belt even while the lower energy (< ~300 keV) electrons do. Two other intriguing points that we will discuss concerning these results are: i) what acceleration mechanism is capable of producing such abundance of relativistic electrons at such large radial distances (X-GSE < -10 RE) in Earth’s magnetotail? and ii) during what conditions (if any) might injections of relativistic electrons be able to penetrate into the outer belt?</p>

scholarly journals Comparison of energetic electron flux and phase space density in the magnetosheath and in the magnetosphere

2012 ◽  
Vol 117 (A5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Bingxian Luo ◽  
Xinlin Li ◽  
Weichao Tu ◽  
Jiancun Gong ◽  
Siqing Liu
Keyword(s):  
Phase Space ◽  
Electron Flux ◽  
Energetic Electron ◽  
Phase Space Density ◽  
Space Density

Phase Space Density Analysis of Outer Radiation Belt Electron Energization and Loss during Geoeffective and Nongeoeffective Sheath Regions

2021 ◽  
Author(s):  
Milla M. H. Kalliokoski ◽  
Emilia Kilpua ◽  
Adnane Osmane ◽  
Allison N Jaynes ◽  
Drew L. Turner ◽  
...  
Keyword(s):  
Phase Space ◽  
Radiation Belt ◽  
Phase Space Density ◽  
Outer Radiation Belt ◽  
Space Density ◽  
Density Analysis

scholarly journals On the storm-time evolution of relativistic electron phase space density in Earth's outer radiation belt

2013 ◽  
Vol 118 (5) ◽  
pp. 2196-2212 ◽  
Author(s):  
D. L. Turner ◽  
V. Angelopoulos ◽  
W. Li ◽  
M. D. Hartinger ◽  
M. Usanova ◽  
...  
Keyword(s):  
Phase Space ◽  
Relativistic Electron ◽  
Time Evolution ◽  
Radiation Belt ◽  
Phase Space Density ◽  
Outer Radiation Belt ◽  
Space Density

scholarly journals Outer radiation belt and inner magnetospheric response to sheath regions of coronal mass ejections: A statistical analysis

2019 ◽  
Author(s):  
Milla M. H. Kalliokoski ◽  
Emilia K. J. Kilpua ◽  
Adnane Osmane ◽  
Drew L. Turner ◽  
Allison N. Jaynes ◽  
...  
Keyword(s):  
Coronal Mass Ejections ◽  
Large Scale ◽  
Electron Flux ◽  
Energetic Electron ◽  
Radial Distance ◽  
Wave Power ◽  
Electron Content ◽  
Interplanetary Coronal Mass Ejections ◽  
Outer Radiation Belt ◽  
The Earth

Abstract. The energetic electron content in the Van Allen radiation belts surrounding the Earth can vary dramatically on several timescales, and these strong electron fluxes present a hazard for spacecraft traversing the belts. The belt response to solar wind driving is yet largely unpredictable and especially the direct response to specific large-scale heliospheric structures has not been considered previously. We investigate the immediate response of electron fluxes in the outer belt to driving by sheath regions preceding interplanetary coronal mass ejections and the associated wave activity in the inner magnetosphere. We consider events from 2012 to 2018 in the Van Allen Probes era to employ the energy and radial distance resolved electron flux observations of the twin spacecraft mission. We perform a statistical study of the events using superposed epoch analysis, where the sheaths are superposed separately from the ejecta and resampled to the same average duration. Our results show that wave power of ultra-low frequency Pc5 and electromagnetic ion cyclotron waves, as measured by a geostationary GOES satellite, is higher during the sheaths than during the ejecta. However, the level of chorus wave power remains approximately the same, despite on average stronger ring current enhancements during the ejecta. Electron flux enhancements are common at low energies ( 4). Distinctively, depletion extends to lower energies at larger distances. We suggest that this L-shell and energy dependent depletion results from magnetopause shadowing dominating the losses at large distances, while wave-particle interactions dominate closer to the Earth. We also show that non-geoeffective sheaths cause significant changes in the outer belt electron fluxes.

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